U.S. patent application number 12/917902 was filed with the patent office on 2012-05-03 for fin-like field effect transistor (finfet) device and method of manufacturing same.
This patent application is currently assigned to TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY, LTD.. Invention is credited to Chih-Hao Chang, Jeff J. Xu.
Application Number | 20120104472 12/917902 |
Document ID | / |
Family ID | 45995713 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120104472 |
Kind Code |
A1 |
Xu; Jeff J. ; et
al. |
May 3, 2012 |
FIN-LIKE FIELD EFFECT TRANSISTOR (FINFET) DEVICE AND METHOD OF
MANUFACTURING SAME
Abstract
A FinFET device and method for fabricating a FinFET device is
disclosed. An exemplary method includes providing a semiconductor
substrate; forming a first fin structure and a second fin structure
over the semiconductor substrate; forming a gate structure over a
portion of the first and second fin structures, such that the gate
structure traverses the first and second fin structures;
epitaxially growing a first semiconductor material on exposed
portions of the first and second fin structures, such that the
exposed portions of the first and second fin structures are merged
together; and epitaxially growing a second semiconductor material
over the first semiconductor material.
Inventors: |
Xu; Jeff J.; (Jhubei City,
TW) ; Chang; Chih-Hao; (Chu-Bei City, TW) |
Assignee: |
TAIWAN SEMICONDUCTOR MANUFACTURING
COMPANY, LTD.
Hsin-Chu
TW
|
Family ID: |
45995713 |
Appl. No.: |
12/917902 |
Filed: |
November 2, 2010 |
Current U.S.
Class: |
257/288 ;
257/E21.409; 257/E29.255; 438/294 |
Current CPC
Class: |
H01L 27/0886 20130101;
H01L 29/165 20130101; H01L 29/66795 20130101; H01L 29/7848
20130101; H01L 29/785 20130101 |
Class at
Publication: |
257/288 ;
438/294; 257/E29.255; 257/E21.409 |
International
Class: |
H01L 29/78 20060101
H01L029/78; H01L 21/336 20060101 H01L021/336 |
Claims
1. A method comprising: providing a semiconductor substrate;
forming a plurality of fins over the semiconductor substrate, the
fins being isolated from each other by an isolation structure;
forming a gate structure over a portion of each fin, such that the
gate structure traverses the plurality of fins; forming a fin
template on exposed portions of the fins; and epitaxially (epi)
growing a semiconductor material over the fin template.
2. The method of claim 1 wherein the forming the fin template
includes epitaxially growing another semiconductor material on
exposed portions of each of the fins, such that the fins are merged
together.
3. The method of claim 2 further including etching back the
isolation structure before forming the fin template.
4. The method of claim 3 further including: forming spacers on
sidewalls of the gate structure; and wherein the etching back the
isolation structure includes using an etching process that
selectively etches the isolation structure.
5. The method of claim 2 wherein: the epitaxially growing the
semiconductor material on exposed portions of the fins includes
epitaxially growing silicon; and the epitaxially growing the
semiconductor material over the fin template includes eptiaxially
growing silicon germanium.
6. The method of claim 1 further including etching back the fin
template before epitaxially growing the semiconductor material over
the fin template.
7. The method of claim 6 wherein: the gate structure separates a
source region and a drain region of each of the fins, the source
and drain regions of each fin defining a channel therebetween; and
the etching back the fin template includes exposing a portion of
the channel of each of the fins.
8. The method of claim 1 wherein the forming the plurality of fins
includes forming the fins having a first material portion and a
second material portion, each of the fins including a source region
and a drain region separated by the gate structure, the source and
drain regions of each fin defining a channel therebetween.
9. The method of claim 8 further including completely removing the
second material portion from the source and drain regions of the
fins before forming the fin template.
10. The method of claim 8 further including partially removing the
second material portion from the source and drain regions of the
fins before forming the fin template.
11. A method comprising: providing a semiconductor substrate;
forming a first fin structure and a second fin structure over the
semiconductor substrate; forming a gate structure over a portion of
the first and second fin structures, such that the gate structure
traverses the first and second fin structures; epitaxially growing
a first semiconductor material on exposed portions of the first and
second fin structures, such that the exposed portions of the first
and second fin structures are merged together; and epitaxially
growing a second semiconductor material over the first
semiconductor material.
12. The method of claim 11 further including: forming an isolation
structure between the first and second fin structures, such that
the first and second fin structures are isolated from one another;
and etching back the isolation structure before epitaxially growing
the first semiconductor material.
13. The method of claim 11 further including etching back the first
semiconductor material before epitaxially growing the second
semiconductor material.
14. The method of claim 11 wherein: the epitaxially growing the
first semiconductor material includes epitaxially growing silicon;
and the epitaxially growing the second semiconductor material
includes epitaxially growing silicon germanium.
15. The method of claim 11 further including removing a portion of
the first and second fin structures before epitaxially growing the
first semiconductor material.
16. The method of claim 15 wherein: the first and second fins
include a first material portion and a second material portion, the
first and second fins each having a source region and a drain
region separated by the gate structure, the source and drain
regions of each fin defining a channel therebetween; and the
removing the portion of the first and second fins includes
completely removing the second material portion from the source and
drain regions of the first and second fins.
17. The method of claim 15 wherein: the first and second fins
include a first material portion and a second material portion, the
first and second fins each having a source region and a drain
region separated by the gate structure, the source and drain
regions of each fin defining a channel therebetween; and the
removing the portion of the first and second fins includes
partially removing the second material portion from the source and
drain regions of the first and second fins.
18. A integrated circuit device comprising: a semiconductor
substrate; a first fin and a second fin disposed over the
semiconductor substrate; an isolation structure disposed between
the first and second fins, such that the first and second fins are
isolated from each other; a gate structure disposed over a portion
of the first and second fins, the gate structure traversing the
first and second fins, thereby separating a source region and a
drain region of the first and second fins; a first epitaxial
semiconductor layer disposed over another portion of the first and
second fins; and a second epitaxial semiconductor layer disposed
over the first epitaxial semiconductor layer, wherein the source
and drain regions of the first and second fins include a portion of
the first and second epitaxial semiconductor layers.
19. The integrated circuit device of claim 18 wherein the source
and drain regions of each of the first and second fins defines a
channel therebetween, the channel being in contact with the first
and second epitaxial semiconductor layers.
20. The integrated circuit device of claim 18 wherein: the first
and second fins include silicon; the first epitaxial semiconductor
layer includes silicon; and the second epitaxial semiconductor
layer includes silicon germanium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present disclosure is related to commonly-assigned U.S.
patent application entitled Fin-Like Field Effect Transistor
(FinFET) Device and Method of Manufacturing Same (Attorney Docket
No. 2010-0693/24061.1546), filed Oct. 18, 2010, the entire
disclosure of which is incorporated herein by reference.
BACKGROUND
[0002] As the semiconductor industry has progressed into nanometer
technology process nodes in pursuit of higher device density,
higher performance, and lower costs, challenges from both
fabrication and design have resulted in the development of three
dimensional designs, such as fin-like field effect transistors
(FinFETs). A typical FinFET is fabricated with a thin "fin" (or fin
structure) extending from a substrate, for example, etched into a
silicon layer of the substrate. The channel of the FinFET is formed
in the vertical fin. A gate is provided over (e.g., wrapping) the
fin. It is beneficial to have a gate on both sides of the channel
allowing gate control of the channel from both sides. FinFET
devices also include strained source/drain features to enhance
carrier mobility and improve device performance. The strained
source/drain features typically use epitaxial (epi) silicon
germanium (SiGe) in p-type devices and epi silicon (Si) in n-type
devices. FinFET devices provide numerous advantages, including
reduced short channel effects and increased current flow. Although
existing FinFET devices and methods for fabricating FinFET devices
have been generally adequate for their intended purposes, as device
scaling down continues, they have not been entirely satisfactory in
all respects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The present disclosure is best understood from the following
detailed description when read with the accompanying figures. It is
emphasized that, in accordance with the standard practice in the
industry, various features are not drawn to scale and are used for
illustration purposes only. In fact, the dimensions of the various
features may be arbitrarily increased or reduced for clarity of
discussion.
[0004] FIG. 1 is a flow chart of a method for fabricating a
fin-like field effect transistor (FinFET) device according to
aspects of the present disclosure.
[0005] FIGS. 2-6 are perspective views of a FinFET device at
various fabrication stages according to the method of FIG. 1.
[0006] FIG. 7 is a flow chart of another method for fabricating a
FinFET device according to aspects of the present disclosure.
[0007] FIGS. 8A, 9A, 10A, and 11A are perspective views of a FinFET
device at various fabrication stages according to the method of
FIG. 7.
[0008] FIGS. 8B, 9B, 10B, and 11B are diagrammatic cross-sectional
views of the FinFET device illustrated in FIGS. 8A, 9A, 10A, and
11A, respectively.
[0009] FIGS. 8C, 9C, 10C, and 11C are diagrammatic cross-sectional
views of the FinFET device illustrated in FIGS. 8A, 9A, 10A, and
11A, respectively.
[0010] FIG. 12 is a flow chart of yet another method for
fabricating a FinFET device according to aspects of the present
disclosure.
[0011] FIGS. 13A, 14A, 15A, and 16A are perspective views of a
FinFET device at various fabrication stages according to the method
of FIG. 12.
[0012] FIGS. 13B, 14B, 15B, and 16B are diagrammatic
cross-sectional views of the FinFET device illustrated in FIGS.
13A, 14A, 15A, and 16A, respectively.
[0013] FIGS. 13C, 14C, 15C, and 16C are diagrammatic
cross-sectional views of the FinFET device illustrated in FIGS.
13A, 14A, 15A, and 16A, respectively.
DETAILED DESCRIPTION
[0014] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the invention. Specific examples of components and arrangements are
described below to simplify the present disclosure. These are, of
course, merely examples and are not intended to be limiting. For
example, the formation of a first feature over or on a second
feature in the description that follows may include embodiments in
which the first and second features are formed in direct contact,
and may also include embodiments in which additional features may
be formed between the first and second features, such that the
first and second features may not be in direct contact. In
addition, the present disclosure may repeat reference numerals
and/or letters in the various examples. This repetition is for the
purpose of simplicity and clarity and does not in itself dictate a
relationship between the various embodiments and/or configurations
discussed.
[0015] FIG. 1 is a flow chart of a method 10 for fabricating an
integrated circuit device according to various aspects of the
present disclosure. In the depicted embodiment, the method 10
fabricates an integrated circuit device that includes a fin-like
field effect transistor (FinFET) device. The method 10 begins at
block 12 where a semiconductor substrate is provided. At block 14,
a first fin and a second fin are formed over the semiconductor
substrate. An isolation structure is formed to isolate the first
and second fins. At block 16, a gate structure is formed over a
portion of the first and second fins. The gate structure traverses
the first and second fins. At block 18, a fin template is formed on
exposed portions of the first and second fins. At block 20, a
semiconductor material is epitaxially grown over the fin template.
The method 10 continues with block 22 where fabrication of the
integrated circuit device is completed. Additional steps can be
provided before, during, and after the method 10, and some of the
steps described can be replaced or eliminated for other embodiments
of the method. The discussion that follows illustrates various
embodiments of an integrated circuit device that can be fabricated
according to the method 10 of FIG. 1.
[0016] FIGS. 2-6 provide various perspective views of a FinFET
device 100, in portion or entirety, at various stages of
fabrication according to the method 10 of FIG. 1. The term FinFET
device refers to any fin-based transistor, such as a fin-based,
multi-gate transistor. The FinFET device 100 may be included in a
microprocessor, memory cell, and/or other integrated circuit
device. FIGS. 2-6 have been simplified for the sake of clarity to
better understand the inventive concepts of the present disclosure.
Additional features can be added in the FinFET device 100, and some
of the features described below can be replaced or eliminated in
other embodiments of the FinFET device 100.
[0017] Referring to FIG. 2, the FinFET device 100 includes a
substrate (wafer) 110. In the depicted embodiment, the substrate
110 is a bulk silicon substrate. Alternatively or additionally, the
substrate 110 includes an elementary semiconductor, such as silicon
or germanium in a crystalline structure; a compound semiconductor,
such as silicon carbide, gallium arsenic, gallium phosphide, indium
phosphide, indium arsenide, and/or indium antimonide; or
combinations thereof. Alternatively, the substrate 110 is a
silicon-on-insulator (SOI) substrate. The SOI substrate can be
fabricated using separation by implantation of oxygen (SIMOX),
wafer bonding, and/or other suitable methods. The substrate 110 may
include various doped regions and other suitable features.
[0018] The FinFET device 100 includes fin structure 115A and 115B
that extend from the substrate 110. In the depicted embodiment, the
fin structures 115A and 115B include fins 120. The fins 120 include
silicon (Si), and accordingly, may also be referred to as Si fins.
The fin structures 115A and 115B may include other material
portions. The fins 120 include a source region, a drain region, and
a channel defined between the source and drain regions. The fins
120 are formed by implementing a lithography and etching process.
For example, beginning with the substrate 110, a lithography and
etching process forms trenches in the substrate 110, thereby
forming fins 120, which extend from the substrate 110. The
lithography process may include photoresist coating (e.g., spin-on
coating), soft baking, mask aligning, exposure, post-exposure
baking, developing the photoresist, rinsing, drying (e.g., hard
baking), other suitable processes, or combinations thereof. For
example, the fin portions 120 may be formed by forming a
photoresist layer (resist) overlying the substrate 110, exposing
the resist to a pattern, performing a post-exposure bake process,
and developing the resist to form a masking element including the
resist. The masking element may then be used to etch the fins 120
into the silicon substrate 110. The etching process may be a dry
etching process, wet etching process, other suitable etching
process, or combinations thereof. For example, the fins 120 may be
etched into the substrate 110 using a reactive ion etch (RIE).
Alternatively, the lithography process could be implemented or
replaced by other methods, such as maskless photolithography,
electron-beam writing, ion-beam writing, and/or nanoimprint
technology. The fins 120 may be formed by a double-patterning
lithography (DPL) process. DPL is a method of constructing a
pattern on a substrate by dividing the pattern into two interleaved
patterns. DPL allows enhanced feature (e.g., fin) density. Various
DPL methodologies may be used including double exposure (e.g.,
using two mask sets), forming spacers adjacent features and
removing the features to provide a pattern of spacers, resist
freezing, and/or other suitable processes. It is noted that the
term "fin structure" in the depicted embodiment refers to
individual fins of the FinFET device 100. However, the term "fin
structure" may also refer to the fins collectively, and thus, fin
structure may also refer to fin structures 115A and 115B
collectively. Further, though the depicted embodiment illustrates
two fins, the FinFET device 100 may include fewer or more fins
depending on design requirements of the FinFET device 100.
[0019] Isolation features 130, such as shallow trench isolation
(STI) structures, surround the fin structures 115A and 115B (in the
depicted embodiment, the fins 120), isolating the fins 120 from
each other and other not-illustrated integrated circuit devices.
The isolation features 130 may be formed by partially filling
trenches surrounding the fins 120 with an insulating material, such
as silicon oxide, silicon nitride, silicon oxynitride, other
suitable material, or combinations thereof. The filled trench may
have a multi-layer structure, for example, a thermal oxide liner
layer with silicon nitride filling the trench. In the depicted
embodiment, the isolation features 130 include an oxide
material.
[0020] The FinFET device 100 includes a gate structure 150. The
gate structure 150 traverses the fins 120, and in the depicted
embodiment, is formed on a central portion of the fins 120. The
gate structure 150 may include a gate dielectric layer and a gate
electrode. The gate dielectric layer includes a dielectric
material, such as silicon oxide, high-k dielectric material, other
suitable dielectric material, or combinations thereof. Examples of
high-k dielectric material include HfO.sub.2, HfSiO, HfSiON, HfTaO,
HfTiO, HfZrO, zirconium oxide, aluminum oxide, hafnium
dioxide-alumina (HfO.sub.2--Al.sub.2O.sub.3) alloy, other suitable
high-k dielectric materials, or combinations thereof. The gate
electrode includes polysilicon and/or a metal including Al, Cu, Ti,
Ta, W, Mo, TaN, NiSi, CoSi, TiN, WN, TiAl, TiAlN, TaCN, TaC, TaSiN,
other conductive materials, or combinations thereof. The gate
structure 150, such as the gate electrode, may be formed in a gate
first or gate last process. The gate structure 150 may include
numerous other layers, for example, capping layers, interface
layers, diffusion layers, barrier layers, hard mask layers, or
combinations thereof.
[0021] The gate structure 150 is formed by a suitable process,
including deposition, lithography patterning, and etching
processes. The deposition processes include chemical vapor
deposition (CVD), physical vapor deposition (PVD), atomic layer
deposition (ALD), high density plasma CVD (HDPCVD), metal organic
CVD (MOCVD), remote plasma CVD (RPCVD), plasma enhanced CVD
(PECVD), low-pressure CVD (LPCVD), atomic layer CVD (ALCVD),
atmospheric pressure CVD (APCVD), plating, other suitable methods,
or combinations thereof. The lithography patterning processes
include photoresist coating (e.g., spin-on coating), soft baking,
mask aligning, exposure, post-exposure baking, developing the
photoresist, rinsing, drying (e.g., hard baking), other suitable
processes, or combinations thereof. Alternatively, the lithography
exposing process is implemented or replaced by other methods, such
as maskless photolithography, electron-beam writing, or ion-beam
writing. In yet another alternative, the lithography patterning
process could implement nanoimprint technology. The etching
processes include dry etching, wet etching, and/or other etching
methods.
[0022] Spacers 152 are disposed on the sidewalls of the gate
structure 150, such as along the gate electrode. The spacers 152
include a dielectric material, such as silicon oxide, silicon
nitride, silicon oxynitride, other suitable material, or
combinations thereof. The spacers may include a multi-layer
structure, such as a multi-layer structure including a silicon
nitride layer and a silicon oxide layer. The spacers are formed by
a suitable process to a suitable thickness. For example, in the
depicted embodiment, spacers 152 may be formed by depositing a
silicon nitride layer and then dry etching the layer to form the
spacers 152 as illustrated in FIG. 2. Before or after forming the
spacers 152, implantation, diffusion, and/or annealing processes
may be performed to form lightly doped source and drain (LDD)
features in the source and drain regions of the fin structures 115A
and 115B.
[0023] Referring to FIG. 3, a process is performed to recess the
isolation features 130. For example, an etching process is applied
to recess the isolation features 130. The etching process is a dry
etching process, wet etching process, other etching process, or
combinations thereof. In the depicted embodiment, the etching
process selectively etches the isolation features 130 and
implements processing parameters that avoid etching the silicon
nitride spacers 152. For example, in the depicted embodiment, the
etching process uses a hydrofluoric acid (HF) etching solution of a
suitable concentration (for example, 100:1). In an example, the HF
solution recesses the isolation features 130 about 100 .ANG..
Alternatively, other etching solutions may be used to effectively
recess the isolation features 130.
[0024] Referring to FIG. 4, a fin template 135 is formed on exposed
portions of the fins 120. For example, the fin template 135 is
formed by merging together the fins 120 of the FinFET device 100.
In the depicted embodiment, merging the fins 120 together is
achieved by epitaxially (epi) growing a semiconductor material on
exposed portions of the fins 120 in the source and drain regions of
the fin structures 115A and 115B. The semiconductor material is
epitaxially grown by an epi process until the fins 120 of the fin
structures 115A and 115B are merged together to form the fin
template 135. The epitaxy process may use CVD deposition techniques
(e.g., vapor-phase epitaxy (VPE) and/or ultra-high vacuum CVD
(UHV-CVD)), molecular beam epitaxy, and/or other suitable
processes. The epitaxy process may use gaseous and/or liquid
precursors. In the depicted embodiment, the fin template 135 is
silicon formed by a silicon epitaxial deposition process. The fin
template 135 can be referred to as a bulk-like Si template.
Alternatively, the fin template 135 could be silicon germanium
(SiGe) formed by a silicon germanium epitaxial deposition process.
The fin template 135 may be doped during deposition (growth) by
adding impurities to the source material of the epitaxy process or
subsequent to its deposition growth process by an ion implantation
process. For example, the epi silicon fin template 135 may be doped
with phosphorous (to form a Si:P epi layer). The doped epitaxial
layer may have a gradient doping profile. A chemical mechanical
polishing (CMP) process may be performed to planarize the fin
template 135. Though the fins 120 and fin template 135 are depicted
separately, it is understood that "fin template" can refer to the
newly grown epi semiconductor material alone (depicted as fin
template 135) or the newly grown epi semiconductor material
combined with the initial fins (depicted as fins 120).
[0025] Referring to FIG. 5, a process is performed to recess the
fin template 135. For example, an etching process is applied to the
fin template 135 to etch back the fin template 135. The etching
process is a dry etching process, wet etching process, other
etching process, or combinations thereof. In an example, the
etching process uses a mixture of HBr, Cl.sub.2, and O.sub.2.
Alternatively, other etching process mixtures may be used to
effectively recess the fin template 135. A radio frequency (RF)
bias power of the etching process may be about 30 Watts (W) to
about 400 W. The fin template 135 is etched back sufficiently to
expose the channels of the fin structures 115A and 115B as
illustrated in FIG. 5. This ensures that later-formed raised source
and drain features (semiconductor material 160) can effectively
introduce strain into the channels of the fins structures 115A and
115B.
[0026] Referring to FIG. 6, a semiconductor material 160 is
epitaxially grown over the fin template 135. In the depicted
embodiment, a semiconductor material is epi grown on the exposed
fin template 135 in the source and drain regions of the fin
structures 115A and 115B. The epi grown semiconductor material 160
generates channel strain for the fin structures 115A and 115B. The
epitaxy process may use CVD deposition techniques (e.g.,
vapor-phase epitaxy (VPE) and/or ultra-high vacuum CVD (UHV-CVD)),
molecular beam epitaxy, and/or other suitable processes. The
epitaxy process may use gaseous and/or liquid precursors. In the
depicted embodiment, the semiconductor material 160 is silicon
germanium (SiGe) formed by a silicon germanium epitaxial deposition
process. Alternatively, the semiconductor material 160 could be
silicon formed by a silicon epitaxial deposition process. The
semiconductor material 160 may be doped during deposition (growth)
by adding impurities to the source material of the epitaxy process
or subsequent to its deposition growth process by an ion
implantation process. A CMP process may be performed to planarize
the semiconductor material 160. The semiconductor material 160 may
be referred to as raised source and drain features of the source
and drain regions of the fin structure 115A and 115B. It should be
noted that the fin template 135 in the source and drain regions of
the fin structures 115A and 115B may also be considered as part of
the raised source and drain features. Before or after forming the
semiconductor material 160, implantation, diffusion, and/or
annealing processes may be performed to form heavily doped source
and drain (HDD) features in the source and drain regions of the fin
structures 115A and 115B.
[0027] Conventional FinFET devices form raised source and drain
features (for example, semiconductor material 160) on unmerged
fins, such as the fins 120 as illustrated in FIG. 2. As technology
nodes continually scale down, a width of the unmerged fins, such as
the fins 120, continues to decrease, for example, to about 15 nm
and below. It has been observed that the raised source and drain
features grown on the exposed surfaces of the unmerged fins, such
as along the width of the unmerged fins, provides insufficient
strain as technology nodes decrease. For example, the strain
provided by the raised source and drain features formed over
unmerged fins tend to relax along the width direction of the
unmerged fins. This can occur because of space between adjacent
unmerged fins (in other words, free space). As the strain (stress)
relaxes in the fin width direction, defects and dislocations may
occur in the raised source and drain features, negatively effecting
device performance. In contrast, to remedy the stress relaxation
issues inherent in conventional FinFET devices, the disclosed
method 10 merges fins 120 together to form the fin template 135 for
FinFET device 100. The method 10 provides a self-aligned
source/drain template growth scheme that can be easily implemented
into integrated circuit processing and provide maximum raised
source and drain features for enhancing FinFET device performance.
In particular, the fin template 135 provides a planar-like source
and drain area for forming the raised source/drain features in the
source and drain regions of the fin structures 115A and 115B. This
provides minimal stress relaxation along the fin width direction
and achieves planar-like channel strain. The disclosed FinFET
device 100 can thus provide maximum strain to the channels of the
fin structures 115A and 115B with limited (or sometimes no) defects
and/or dislocations.
[0028] The FinFET device 100 may include additional features, which
may be formed by subsequent processing. For example, silicide
features may be formed in the source and drain regions of the fin
structures 115A and 115B. The silicide features may be formed by a
silicidation process, such as a self-aligned silicide (salicide)
process. Various contacts/vias/lines and multilayer interconnect
features (e.g., metal layers and interlayer dielectrics) may be
formed over the substrate 110, configured to connect the various
features or structures of the FinFET device 100. The additional
features may provide electrical interconnection to the device 100
including the gate structure 150. For example, a multilayer
interconnection includes vertical interconnects, such as
conventional vias or contacts, and horizontal interconnects, such
as metal lines. The various interconnection features may implement
various conductive materials including copper, tungsten, and/or
silicide. In one example, a damascene and/or dual damascene process
is used to form a copper related multilayer interconnection
structure.
[0029] FIG. 7 is a flow chart of a method 30 for fabricating an
integrated circuit device according to various aspects of the
present disclosure. In the depicted embodiment, the method 30
fabricates an integrated circuit device that includes a fin-like
field effect transistor (FinFET) device. The method 30 begins at
block 32 where a semiconductor substrate is provided. At block 34,
a first fin structure and a second fin structure is formed over the
semiconductor substrate. More specifically, a first material
portion of the first and second fin structures is formed over the
semiconductor substrate, and a second material portion of the first
and second fin structures is formed over the first material
portion. At block 36, a gate structure is formed over a portion of
the first and second fin structures. The gate structure traverses
the first and second fin structures, separating a source region and
a drain region of the first and second fin structures. A channel is
defined between the source and drain regions of the first and
second fin structures. At block 38, the second material portion is
completely removed from the source and drain regions of the first
and second fin structures. At block 40, the first material portions
of the source and drain regions of the first and second fin
structures are merged together to form a fin template. At block 42,
a third material portion is formed over the fin template in the
source and drain regions of the first and second fin structures.
The method 30 continues with block 44 where fabrication of the
integrated circuit device is completed. Additional steps can be
provided before, during, and after the method 30, and some of the
steps described can be replaced or eliminated for other embodiments
of the method.
[0030] FIGS. 8A-8C, 9A-9C, 10A-10C, and 11A-11C provide various
views of a FinFET device 200, in portion or entirety, at various
stages of fabrication according to the method 30 of FIG. 7. The
term FinFET device refers to any fin-based transistor, such as a
fin-based, multi-gate transistor. The FinFET device 200 may be
included in a microprocessor, memory cell, and/or other integrated
circuit device. In the depicted embodiment, the FinFET device 200
is a p-type metal-oxide-semiconductor (PMOS) FinFET device. FIGS.
8A-8C, 9A-9C, 10A-10C, and 11A-11C have been simplified for the
sake of clarity to better understand the inventive concepts of the
present disclosure. Additional features can be added in the FinFET
device 200, and some of the features described below can be
replaced or eliminated in other embodiments of the FinFET device
200.
[0031] FIG. 8A is a perspective view of the FinFET device 200, FIG.
8B is a diagrammatic cross-sectional view of the FinFET device 200
taken along line 8B-8B in FIG. 8A, and FIG. 8C is a diagrammatic
cross-sectional view of the FinFET device 200 taken along line
8C-8C in FIG. 8A. The FinFET device 200 includes a substrate
(wafer) 210. In the depicted embodiment, the substrate 210 is a
bulk silicon substrate. Alternatively or additionally, the
substrate 210 includes an elementary semiconductor, such as silicon
or germanium in a crystalline structure; a compound semiconductor,
such as silicon carbide, gallium arsenic, gallium phosphide, indium
phosphide, indium arsenide, and/or indium antimonide; or
combinations thereof. Alternatively, the substrate 210 is a
silicon-on-insulator (SOI) substrate. The SOI substrate can be
fabricated using separation by implantation of oxygen (SIMOX),
wafer bonding, and/or other suitable methods. The substrate 210 may
include various doped regions and other suitable features.
[0032] The FinFET device 200 includes fin structures 215A and 215B
that extend from the substrate 210. In the depicted embodiment, the
fin structures 215A and 215B include fin portions 220 and 230. The
fin portions 220 include silicon (Si), and the fin portions 230
include silicon germanium (SiGe). The SiGe concentration of the fin
portion 230 may be represented by Si.sub.1-xGe.sub.x, where x
represents Ge composition in atomic percent. In the depicted
embodiment, x is less than or equal to 1, and greater than or equal
to 0. FIG. 8C is a diagrammatic cross-sectional view of the FinFET
device 200 taken along a channel of the fin structure 215A, which
depicts a source region S and a drain region D of the fin structure
215A. A channel region C is defined between the source and drain
regions. Fin structure 215B similarly includes source, drain, and
channel regions. It is noted that the term "fin structure" in the
depicted embodiment refers to individual fins of the FinFET device
200. However, the term "fin structure" may also refer to the fins
collectively, and thus, fin structure may also refer collectively
to fin structures 215A and 215B. Further, though the depicted
embodiment illustrates two fins, the FinFET device 200 may include
fewer or more fins depending on design requirements of the FinFET
device 200.
[0033] The fin structures 215A and 215B, including fin portions 220
and 230, are formed by a suitable process. In one example, the fin
structures 215A and 215B are formed by implementing a lithography
and etching process to form the fin portion 220, and implementing
an epitaxial growth process to form the fin portion 230. For
example, beginning with the substrate 210, a lithography and
etching process forms trenches in the substrate 210, thereby
forming fin portions 220 (referred to as Si fin portions) of the
fin structures 215A and 215B, which extend from the substrate 210.
The lithography process may include photoresist coating (e.g.,
spin-on coating), soft baking, mask aligning, exposure,
post-exposure baking, developing the photoresist, rinsing, drying
(e.g., hard baking), other suitable processes, or combinations
thereof. For example, the fin portions 220 may be formed by forming
a photoresist layer (resist) overlying the substrate 210, exposing
the resist to a pattern, performing a post-exposure bake process,
and developing the resist to form a masking element including the
resist. The masking element may then be used to etch the fin
portions 220 into the silicon substrate 210. The etching process
may be a dry etching process, wet etching process, other suitable
etching process, or combinations thereof. For example, the fin
portions 220 may be etched into the substrate 210 using a reactive
ion etch (RIE). Alternatively, the lithography process could be
implemented or replaced by other methods, such as maskless
photolithography, electron-beam writing, ion-beam writing, and/or
nanoimprint technology. The fin portions 220 may be formed by a DPL
process, which is described above.
[0034] After the fin portions 220 are etched into the substrate
210, an insulation layer can be formed over the substrate 210,
including over the fin portions 220. The insulation layer fills the
trenches in the substrate 210. Portions of the insulation layer are
then removed to form openings in the insulation layer that expose a
top surface of the fin portions 220. A semiconductor material can
be epitaxially (epi) grown on the exposed surfaces of the fin
portions 220 to form fin portions 230 of the fin structures 215A
and 215B. The epitaxy process may use CVD deposition techniques
(e.g., vapor-phase epitaxy (VPE) and/or ultra-high vacuum CVD
(UHV-CVD)), molecular beam epitaxy, and/or other suitable
processes. The epitaxy process may use gaseous and/or liquid
precursors, which interact with the composition of the fin portions
220 (in other words, interact with the Si fin portions 220). In the
depicted embodiment, the fin portions 230 include silicon germanium
(SiGe) formed by a silicon germanium epitaxial deposition process.
Alternatively, the fin portions 230 could comprise epitaxially
grown silicon. The fin portions 230 may be doped during deposition
(growth) by adding impurities to the source material of the epitaxy
process or subsequent to its deposition growth process by an ion
implantation process. For example, an epi silicon fin portion may
be doped with phosphorous (to form a Si:P epi layer). The doped
epitaxial layer may have a gradient doping profile. A CMP process
may be performed to planarize the fin portions 230. Thereafter, the
remaining insulation layer may be subjected to an etch back
process, or a CMP process, thereby forming isolation features (such
as isolation features 240).
[0035] In another example, the fin structures 215A and 215B are
formed by implementing a lithography and etching process to form
the fin portion 220, and implementing a condensation process to
form the fin portion 230. The condensation process may implement
the methods described in U.S. patent application Ser. No.
12/702,862, entitled Bottom-Notched SiGe FinFET Formation by
Condensation Method, filed Feb. 9, 2010, which is hereby
incorporated by reference in its entirety. For example, beginning
with the substrate 210, a lithography and etching process forms
trenches in the substrate 210, thereby forming fin portions 220
(referred to as Si fin portions) of the fin structures 215A and
215B, which extend from the substrate 210. The lithography and
etching process may be similar to that described above. Thereafter,
an insulation layer can be formed over the substrate 210, filling
in the trenches. The insulation layer may be subjected to an etch
back process to form isolation features (such as isolation features
240). A semiconductor material is then epitaxially (epi) grown on
the exposed fin portions 220. For example, SiGe is grown on the
exposed fin portions 220 by an epitaxial process, similar to the
epitaxial processes described above. Thereafter, a SiGe
condensation process causes Ge from the SiGe material to diffuse
into fin portions 220 (Si fins), forming fin portions 230.
Thereafter, the isolation features may be subjected to an etch back
process, or a CMP process.
[0036] Isolation features 240, such as shallow trench isolation
(STI) structures, surround the fin structures 215A and 215B,
isolating the fin structures 215A and 215B from each other and
other not-illustrated integrated circuit devices. The isolation
features 240 may be formed by partially filling trenches
surrounding the fin structures 215A and 215B with an insulating
material, such as silicon oxide, silicon nitride, silicon
oxynitride, other suitable material, or combinations thereof. The
filled trench may have a multi-layer structure, for example, a
thermal oxide liner layer with silicon nitride filling the
trench.
[0037] The FinFET device 200 includes a gate structure 250. The
gate structure 250 traverses the fin structures 215A and 215B, and
in the depicted embodiment, is formed on a central portion of the
fin structures 215A and 215B. The gate structure 250 may include a
gate dielectric layer and a gate electrode. The gate dielectric
layer includes a dielectric material, such as silicon oxide, high-k
dielectric material, other suitable dielectric material, or
combinations thereof. Examples of high-k dielectric material
include HfO.sub.2, HfSiO, HfSiON, HfTaO, HfTiO, HfZrO, zirconium
oxide, aluminum oxide, hafnium dioxide-alumina
(HfO.sub.2--Al.sub.2O.sub.3) alloy, other suitable high-k
dielectric materials, or combinations thereof. The gate electrode
includes polysilicon and/or a metal including Al, Cu, Ti, Ta, W,
Mo, TaN, NiSi, CoSi, TiN, WN, TiAl, TiAlN, TaCN, TaC, TaSiN, other
conductive materials, or combinations thereof. The gate structure
250, such as the gate electrode, may be formed in a gate first or
gate last process. The gate structure 250 may include numerous
other layers, for example, capping layers, interface layers,
diffusion layers, barrier layers, hard mask layers, or combinations
thereof.
[0038] The gate structure 250 is formed by a suitable process,
including deposition, lithography patterning, and etching
processes. The deposition processes include CVD, PVD, ALD, HDPCVD,
MOCVD, RPCVD, PECVD, LPCVD, ALCVD, APCVD, plating, other suitable
methods, or combinations thereof. The lithography patterning
processes include photoresist coating (e.g., spin-on coating), soft
baking, mask aligning, exposure, post-exposure baking, developing
the photoresist, rinsing, drying (e.g., hard baking), other
suitable processes, or combinations thereof. Alternatively, the
lithography exposing process is implemented or replaced by other
methods, such as maskless photolithography, electron-beam writing,
and ion-beam writing. In yet another alternative, the lithography
patterning process could implement nanoimprint technology. The
etching processes include dry etching, wet etching, and/or other
etching methods.
[0039] Spacers (not illustrated) may be disposed on the sidewalls
of the gate structure 250, such as along the gate electrode. The
spacers may be similar to spacers 152 described above with
reference to FIG. 2. For example, the spacers include a dielectric
material, such as silicon oxide, silicon nitride, silicon
oxynitride, other suitable material, or combinations thereof. The
spacers may include a multi-layer structure, such as a multi-layer
structure including a silicon nitride layer and a silicon oxide
layer. The spacers are formed by a suitable process to a suitable
thickness. For example, spacers may be formed by depositing silicon
nitride and silicon oxide layers and then dry etching the layers to
form the spacers. Before or after the spacers are formed,
implantation, diffusion, and/or annealing processes may be
performed to form LDD features in the source and drain regions of
the fin structures 215A and 215B.
[0040] FIG. 9A is a perspective view of the FinFET device 200, FIG.
9B is a diagrammatic cross-sectional view of the FinFET device 200
taken along line 9B-9B in FIG. 9A, and FIG. 9C is a diagrammatic
cross-sectional view of the FinFET device 200 taken along line
9C-9C in FIG. 9A. In FIGS. 9A-9C, the fin portions 230 are
completely removed from the source and drain regions of the fin
structures 215A and 215B. More specifically, an etching process
completely removes the fin portions 230 from the source and drain
regions of the fin structures 215A and 215B, exposing the fin
portions 220. The etching process is a dry etching process, wet
etching process, other etching process, or combinations thereof. In
an example, the etching process uses a mixture of HBr, Cl.sub.2,
and O.sub.2. Alternatively, other etching process mixtures may be
used to effectively remove the fin portions 230. A radio frequency
(RF) bias power of the etching process may be about 30 Watts (W) to
about 400 W. A lithography and etching process may be implemented
to provide a protective layer over various features of the FinFET
device 200 (for example, the gate structure 250 and/or isolation
features 240) to prevent the protected features from being affected
by the etching process. As illustrated in FIG. 9C, the fin portion
230 remains in the channel of the fin structures 215A and 215B,
confined by the gate structure 250. The removed fin portions 230
form trenches in the source and drain regions of the fin structures
215A and 215B. The trench sidewalls may be defined by fin portions
220, isolation features 240, remaining fin portion 230 in the
channel region, and/or protective layer (if formed). In the
depicted embodiment, a depth (d.sub.1) of the trenches extends from
an initial top surface of the fin portions 230 to a top, exposed
surface of the fin portion 220. Where a protective layer is
provided, d.sub.1 may extend from a top surface of the protective
layer to the top, exposed surface of the fin portion 220. Other
means of determining the trench depth may be used.
[0041] FIG. 10A is a perspective view of the FinFET device 200,
FIG. 10B is a diagrammatic cross-sectional view of the FinFET
device 200 taken along line 10B-10B in FIG. 10A, and FIG. 10C is a
diagrammatic cross-sectional view of the FinFET device 200 taken
along line 10C-10C in FIG. 10A. In FIGS. 10A-10C, the fin portions
220 in the source and drain regions of the fin structures 215A and
215B are merged together to form a fin template 280. For example,
the fin template 280 may be formed by a process similar to that
described above with reference to FIG. 5. In the depicted
embodiment, a semiconductor material is epitaxially (epi) grown on
the exposed fin portions 220 in the source and drain regions, until
the fin portions 220 of the fin structures 215A and 215B are merged
together to form the fin template 280. The epitaxy process may use
CVD deposition techniques (e.g., VPE and/or UHV-CVD), molecular
beam epitaxy, and/or other suitable processes. The epitaxy process
may use gaseous and/or liquid precursors. In the depicted
embodiment, the fin template 280 is silicon formed by a silicon
epitaxial deposition process. Alternatively, the fin template 280
could be silicon germanium (SiGe) formed by a silicon germanium
epitaxial deposition process. The fin template 280 may be doped
during deposition (growth) by adding impurities to the source
material of the epitaxy process or subsequent to its deposition
growth process by an ion implantation process. For example, an epi
silicon fin portion may be doped with phosphorous (to form a Si:P
epi layer). The doped epitaxial layer may have a gradient doping
profile. A CMP process may be performed to planarize the fin
template 280. Though the fin template 280 and fin portions 220 are
depicted separately, it is understood that "fin template" can refer
to the newly grown epi semiconductor material alone (depicted as
fin template 280) or the newly grown epi semiconductor material
combined with the initial fin portions (depicted as fin portions
220). Similar to the fin template 135 described above with
reference to FIGS. 2-6, the fin template 280 can minimize stress
relaxation along a width of the fin structures 215A and 215B,
maximizing strain to the channels of fin structures 215A and 215B
and enhancing device performance.
[0042] FIG. 11A is a perspective view of the FinFET device 200,
FIG. 11B is a diagrammatic cross-sectional view of the FinFET
device 200 taken along line 11B-11B in FIG. 11A, and FIG. 11C is a
diagrammatic cross-sectional view of the FinFET device 200 taken
along line 11C-11C in FIG. 11A. In FIGS. 11A-11C, a fin portion 285
is formed over the fin template 280, providing the fin structures
215A and 215B with fin portion 285. For example, a semiconductor
material is epitaxially (epi) grown on the fin template 285. The
epitaxy process may use CVD deposition techniques (e.g., VPE and/or
UHV-CVD), molecular beam epitaxy, and/or other suitable processes.
The epitaxy process may use gaseous and/or liquid precursors, which
interact with the composition of the fin template 280 (in other
words, interact with the Si fin template 280). In the depicted
embodiment, the fin portion 285 is silicon germanium (SiGe) formed
by a silicon germanium epitaxial deposition process. The SiGe
concentration of the fin portion 285 is represented by
Si.sub.1-yGe.sub.y, where y represents Ge composition in atomic
percent. In the depicted embodiment, y is less than or equal to 1,
and greater than or equal to 0. The fin portion 285 may be doped
during deposition (growth) by adding impurities to the source
material of the epitaxy process or subsequent to its deposition
growth process by an ion implantation process. The doped epitaxial
layer may have a gradient doping profile. A CMP process may be
performed to planarize the fin portion 285. Further, before or
after forming the fin portion 285, implantation, diffusion, and/or
annealing processes may be performed to form HDD features in the
source and drain regions of the fin structures 215A and 215B.
[0043] As illustrated in FIGS. 11A-11C, the fin structures 215A and
215B include fin portions 220, fin portions 230, fin template 280,
and fin portions 285. More specifically, the source and drain
regions of the fin structures 215A and 215B include fin portions
220, fin template 280, and fin portions 285. The channel of the fin
structures 215A and 215B includes fin portion 220 and fin portion
230. The fin template 280 and/or fin portions 285 in the source and
drain regions of the fin structures 215A and 215B are alternatively
referred to as strained source and drain features of the FinFET
device 200. In the depicted embodiment, fin portions 220 include
Si, fin template 280 includes Si, fin portions 230 include
Si.sub.1-xGe.sub.x, and fin portions 285 include
Si.sub.1-yGe.sub.y. The fin portions 285 provide compressive stress
to the channel of the fin structures 215A and 215B, enhancing hole
mobility in the PMOS FinFET device 200. In the depicted embodiment,
y is independent of x in PMOS FinFET device 200. Accordingly, the
fin portions 285 may include any Ge concentration and still achieve
the compressive strain desired for PMOS FinFET devices. By forming
the fin portions 285 over the Si fin portions (fin template 280),
compressive strain is achieved regardless of the SiGe concentration
of the channel. For example, compressive strain from the Si fin
template 280 on the Si.sub.1-yGe.sub.y fin portions 285 cause the
fin portions 285 to push/stress the channel/fin portions 230,
providing uniaxial stress to the channel of the FinFET device
200.
[0044] The FinFET device 200 may include additional features, which
may be formed by subsequent processing. For example, silicide
features may be formed in the source and drain regions of the fin
structures 215A and 215B, specifically on fin portions 285. The
silicide features may be formed by a silicidation process, such as
a self-aligned silicide (salicide) process. Various
contacts/vias/lines and multilayer interconnect features (e.g.,
metal layers and interlayer dielectrics) may be formed over the
substrate 210, configured to connect the various features or
structures of the FinFET device 200. The additional features may
provide electrical interconnection to the device 200 including the
gate structures 250. For example, a multilayer interconnection
includes vertical interconnects, such as conventional vias or
contacts, and horizontal interconnects, such as metal lines. The
various interconnection features may implement various conductive
materials including copper, tungsten, and/or silicide. In one
example, a damascene and/or dual damascene process is used to form
a copper related multilayer interconnection structure.
[0045] FIG. 12 is a flow chart of a method 50 for fabricating an
integrated circuit device according to various aspects of the
present disclosure. In the depicted embodiment, the method 50
fabricates an integrated circuit device that includes a FinFET
device. The method 50 begins at block 52 where a semiconductor
substrate is provided. At block 54, a first fin structure and a
second fin structure is formed over the semiconductor substrate.
More specifically, a first material portion of the first and second
fin structures is formed over the semiconductor substrate, and a
second material portion of the first and second fin structures is
formed over the first material portion. At block 56, a gate
structure is formed over a portion of the first and second fin
structures. The gate structure traverses the first and second fin
structures, separating a source region and a drain region of the
first and second fin structures. A channel is defined between the
source and drain regions of the first and second fin structures. At
block 58, the second material portion is partially removed from the
source and drain regions of the first and second fin structures. At
block 60, remaining second material portions in the source and
drain regions of the first and second fin structures are merged
together to form a fin template. At block 62, a third material
portion is formed over the fin template in the source and drain
regions of the first and second fin structures. The method 600
continues with block 64 where fabrication of the integrated circuit
device is completed. Additional steps can be provided before,
during, and after the method 50, and some of the steps described
can be replaced or eliminated for other embodiments of the
method.
[0046] FIGS. 13A-13C, 14A-14C, 15A-15C, and 16A-16C provide various
views of a FinFET device 400, in portion or entirety, at various
stages of fabrication according to the method 50 of FIG. 12. The
FinFET device 400 may be included in a microprocessor, memory cell,
and/or other integrated circuit device. In the depicted embodiment,
the FinFET device 400 is an NMOS FinFET device. The FinFET device
400 of 13A-13C, 14A-14C, 15A-15C, and 16A-16C is similar in many
respects to the FinFET device 200 of FIGS. 8A-8C, 9A-9C, 10A-10C,
and 11A-11C. Accordingly, similar features in FIGS. 8A-8C, 9A-9C,
10A-10C, 11A-11C, 13A-13C, 14A-14C, 15A-15C, and 16A-16C are
identified by the same reference numerals for clarity and
simplicity. FIGS. 13A-13C, 14A-14C, 15A-15C, and 16A-16C have been
simplified for the sake of clarity to better understand the
inventive concepts of the present disclosure. Additional features
can be added in the FinFET device 400, and some of the features
described below can be replaced or eliminated in other embodiments
of the FinFET device 400.
[0047] FIG. 13A is a perspective view of the FinFET device 400,
FIG. 13B is a diagrammatic cross-sectional view of the FinFET
device 400 taken along line 13B-13B in FIG. 13A, and FIG. 13C is a
diagrammatic cross-sectional view of the FinFET device 400 taken
along line 13C-13C in FIG. 13A. The FinFET device 400 includes the
substrate 210, fin structures 215A and 215B including fin portions
220 and 230, isolation features 240, and gate structure 250. The
fin structures 215A and 215B include a source region, a drain
region, and a channel defined between the source and drain
regions.
[0048] FIG. 14A is a perspective view of the FinFET device 400,
FIG. 14B is a diagrammatic cross-sectional view of the FinFET
device 400 taken along line 14B-14B in FIG. 14A, and FIG. 14C is a
diagrammatic cross-sectional view of the FinFET device 400 taken
along line 14C-14C in FIG. 14A. In FIGS. 14A-14C, the fin portion
230 is removed from the source and drain regions of the fin
structures 215A and 215B. In contrast to the FinFET device 200 of
FIGS. 9A-9C, in the depicted embodiment, an etching process
partially removes the fin portions 230 from the source and drain
regions of the fin structures 215A and 215B. Accordingly, some of
the fin portions 230 remains in the source and drain regions. The
etching process is a dry etching process, wet etching process,
other etching process, or combinations thereof. In an example, the
etching process uses a mixture of HBr, Cl.sub.2, and O.sub.2.
Alternatively, other etching process mixtures may be used to
partially remove fin portions 230. A radio frequency (RF) bias
power of the etching process may be about 30 Watts (W) to about 400
W. A lithography and etching process may be implemented to provide
a protective layer over various features of the FinFET device 400
(for example, the gate structure 250 and/or isolation features 240)
to prevent the protected features from being affected by the
etching process. As illustrated in FIG. 14C, the fin portion 230
remains in the channel of the fin structures 215A and 215B,
confined by the gate structure 250, and some of the fin portions
230 remains in the source and drain regions. The removed fin
portions 230 can form trenches in the source and drain regions of
the fin structures 215A and 215B. The trench sidewalls may be
defined by remaining fin portions 230 (in the source, drain, and
channel regions), isolation features 240, and/or protective layer
(if formed). In the depicted embodiment, a depth (d.sub.2) of the
trenches extends from an initial top surface of the fin portions
230 to a top, exposed surface of the fin portions 230. Where a
protective layer is provided, d.sub.2 may extend from a top surface
of the protective layer to the top, exposed surface of the fin
portions 230. The depth d.sub.1 indicates the depth of the trenches
in the source and drain regions of the FinFET device 200.
Considering d.sub.1 and d.sub.2, the FinFET device 200 has a deeper
trench (or recess) than the FinFET device 400. As will be described
further below, the trench depth can be controlled to achieve
various source and drain features for the fin structures, such that
different kinds of channel strain can be achieved for different
FinFET devices.
[0049] FIG. 15A is a perspective view of the FinFET device 400,
FIG. 15B is a diagrammatic cross-sectional view of the FinFET
device 400 taken along line 15B-15B in FIG. 15A, and FIG. 15C is a
diagrammatic cross-sectional view of the FinFET device 400 taken
along line 15C-15C in FIG. 15A. In FIGS. 15A-15C, the fin portions
230 remaining in the source and drain regions of the fin structures
215A and 215B are merged together to form a fin template 290. For
example, the fin template 290 may be formed by a process similar to
that described above with reference to FIGS. 10A-10C. In the
depicted embodiment, a semiconductor material is epitaxially (epi)
grown on the fin portions 230 remaining in the source and drain
regions. The semiconductor material is epitaxially grown until the
fin portions 230 of the fin structures 215A and 215B are merged
together to form the fin template 290. Though the fin template 290
and fin portions 230 remaining in the source and drain regions are
depicted separately, "fin template" may refer to the newly grown
epi semiconductor material alone (depicted as fin template 290) or
or the newly grown epi semiconductor material combined with the
initial fin portions (depicted as fin portions 230 remaining in the
source and drain regions). The epitaxy process may use CVD
deposition techniques (e.g., VPE and/or UHV-CVD), molecular beam
epitaxy, and/or other suitable processes. The epitaxy process may
use gaseous and/or liquid precursors. In the depicted embodiment,
the fin template 290 includes silicon germanium (SiGe) formed by a
silicon germanium epitaxial deposition process. Alternatively, the
fin template 290 could include epitaxially grown silicon. The fin
template 290 may be doped during deposition (growth) by adding
impurities to the source material of the epitaxy process or
subsequent to its deposition growth process by an ion implantation
process. The doped epitaxial layer may have a gradient doping
profile. A CMP process may be performed to planarize the fin
template 290. Similar to the fin template 135 described above with
reference to FIGS. 2-6, the fin template 290 can minimize stress
relaxation along a width of the fin structures 215A and 215B,
maximizing strain to the channels of fin structures 215A and 215B
and enhancing device performance.
[0050] FIG. 16A is a perspective view of the FinFET device 400,
FIG. 16B is a diagrammatic cross-sectional view of the FinFET
device 400 taken along line 16B-16B in FIG. 16A, and FIG. 16C is a
diagrammatic cross-sectional view of the FinFET device 400 taken
along line 16C-16C in FIG. 16A. In FIGS. 16A-16C, a fin portion 295
is formed over the fin template 290, providing the fin structures
215A and 215B with the fin portion 295. For example, a
semiconductor material is epitaxially (epi) grown on the fin
template 290. The epitaxy process may use CVD deposition techniques
(e.g., VPE and/or UHV-CVD), molecular beam epitaxy, and/or other
suitable processes. The epitaxy process may use gaseous and/or
liquid precursors. In the depicted embodiment, the fin portion 295
includes epitaxially grown SiGe. The SiGe concentration of the fin
portion 295 may be represented by Si.sub.1-zGe.sub.z, where z
represents Ge composition in atomic percent. In the depicted
embodiment, z is less than or equal to 1, and greater than or equal
to 0. Alternatively, the fin portion 295 could include epitaxially
grown Si. The fin portion 295 may be doped during deposition
(growth) by adding impurities to the source material of the epitaxy
process or subsequent to its deposition growth process by an ion
implantation process. The doped epitaxial layer may have a gradient
doping profile. A CMP process may be performed to planarize the fin
portion 295. Further, before or after forming the fin portion 295,
implantation, diffusion, and/or annealing processes may be
performed to form HDD features in the source and drain regions of
the fin structures 215A and 215B.
[0051] As illustrated in FIGS. 16A-16C, the fin structures 215A and
215B include fin portions 220, fin portions 230, fin template 290,
and fin portions 295. More specifically, the source and drain
regions of the fin structures 215A and 215B include fin portions
220, 230, 290, and 295. The channel of the fin structures 215A and
215B includes fin portions 220 and 230. The fin portions 230, 290,
and/or 295 in the source and drain regions are alternatively
referred to as strained source and drain features of the FinFET
device 400. In the depicted embodiment, fin portions 220 include
Si, fin portions 230 and 290 include Si.sub.1-xGe.sub.x, and fin
portions 295 include Si.sub.1-zGe.sub.z, where z is less than x.
The fin portions 230, 290, and 295 provide tensile stress to the
channel of the fins structures 215A and 215B, enhancing electron
mobility in the channel of the NMOS FinFET device 400.
[0052] The FinFET device 400 may include additional features, which
may be formed by subsequent processing. For example, silicide
features may be formed in the source and drain regions of the fin
structures 215A and 215B, specifically on fin portions 295. The
silicide features may be formed by a silicidation process, such as
a self-aligned silicide (salicide) process. Various
contacts/vias/lines and multilayer interconnect features (e.g.,
metal layers and interlayer dielectrics) may be formed over the
substrate 210, configured to connect the various features or
structures of the FinFET device 400. The additional features may
provide electrical interconnection to the device 400 including the
gate structure 250. For example, a multilayer interconnection
includes vertical interconnects, such as conventional vias or
contacts, and horizontal interconnects, such as metal lines. The
various interconnection features may implement various conductive
materials including copper, tungsten, and/or silicide. In one
example, a damascene and/or dual damascene process is used to form
a copper related multilayer interconnection structure.
[0053] Thus, the present disclosure provides integrated circuit
devices that can exhibit maximized strain to their channels, and
methods for fabricating the integrated circuit devices with
maximized strain. Maximized strain can be achieved by incorporating
a fin template in the integrated circuit devices. It is understood
that different embodiments may have different advantages, and that
no particular advantage is necessarily required of any embodiment.
It should also be noted that the FinFET device 100, PMOS FinFET
device 200, and/or NMOS FinFET device 400 can be fabricated in a
single integrated circuit device using the methods 10, 30, and 50
described above. Referring to FinFET devices 200 and 400, by
controlling source and drain trench depth (for example, d.sub.1 and
d.sub.2) for the epi source and drain features, strain for both
PMOS and NMOS FinFET devices can be achieved and optimized. For
example, as described above, fin portions 230 are completely
removed from the source and drain regions of the fin structures
215A and 215B in FinFET device 200, yet are partially removed from
the source and drain regions of the fin structures 215A and 215B in
FinFET device 400. This provides different starting substrates for
forming the fin templates, such that different types of strain can
be achieved. Accordingly, the trench depth can be tuned to
independently optimize performance of each FinFET device in an
integrated circuit device. Further, the fin templates in the PMOS
and NMOS FinFET devices can minimize stress relaxation along a
width of the fin structures.
[0054] The present disclosure provides for many different
embodiments. For example, the present disclosure provides methods
for fabricating an integrated circuit device. In an embodiment, a
method includes providing a semiconductor substrate; forming a
plurality of fins over the semiconductor substrate, the fins being
isolated from each other by an isolation structure; forming a gate
structure over a portion of each fin, such that the gate structure
traverses the plurality of fins; forming a fin template on exposed
portions of the fins; and epitaxially (epi) growing a semiconductor
material over the fin template. Forming the fin template can
include epitaxially growing another semiconductor material on
exposed portions of each of the fins, such that the fins are merged
together. The method can further include etching back the isolation
structure before forming the fin template. The method can further
include forming spacers on sidewalls of the gate structure. The
etching back of the isolation structure may use an etching process
that selectively etches the isolation structure. In an example,
epitaxially growing the semiconductor material on exposed portions
of the fins includes epitaxially growing silicon, and epitaxially
growing the semiconductor material over the fin template includes
eptiaxially growing silicon germanium.
[0055] The method may further include etching back the fin template
before epitaxially growing the semiconductor material over the fin
template. In an example, the gate structure separates a source
region and a drain region of each of the fins, wherein a channel is
defined between the source and drain regions of each fin. Etching
back the fin template may include exposing a portion of the channel
of each of the fins. In an example, forming the plurality of fins
includes forming the fins having a first material portion and a
second material portion, each of the fins including a source region
and a drain region separated by the gate structure, wherein the
source and drain regions of each fin define a channel therebetween.
The method may include completely removing the second material
portion from the source and drain regions of the fins before
forming the fin template and/or partially removing the second
material portion from the source and drain regions of the fins
before forming the fin template.
[0056] In another embodiment, a method includes providing a
semiconductor substrate; forming a first fin structure and a second
fin structure over the semiconductor substrate; forming a gate
structure over a portion of the first and second fin structures,
such that the gate structure traverses the first and second fin
structures; epitaxially growing a first semiconductor material on
exposed portions of the first and second fin structures, such that
the exposed portions of the first and second fin structures are
merged together; and epitaxially growing a second semiconductor
material over the first semiconductor material. The method may
further include forming an isolation structure between the first
and second fin structures, such that the first and second fin
structures are isolated from one another, and etching back the
isolation structure before epitaxially growing the first
semiconductor material. The method may include etching back the
first semiconductor material before epitaxially growing the second
semiconductor material. In an example, the epitaxially growing the
first semiconductor material includes epitaxially growing silicon,
and the epitaxially growing the second semiconductor material
includes epitaxially growing silicon germanium. The method may
include removing a portion of the first and second fin structures
before epitaxially growing the first semiconductor material. In an
example, the first and second fins include a first material portion
and a second material portion, the first and second fins each have
a source region and a drain region separated by the gate structure,
and the source and drain regions of each fin defining a channel
therebetween. In this example, removing the portion of the first
and second fins may include completely removing the second material
portion from the source and drain regions of the first and second
fins and/or partially removing the second material portion from the
source and drain regions of the first and second fins.
[0057] An integrated circuit device is formed by the methods
described herein. In an embodiment, the integrated circuit device
includes a semiconductor substrate; a first fin and a second fin
disposed over the semiconductor substrate; an isolation structure
disposed between the first and second fins, such that the first and
second fins are isolated from each other; a gate structure disposed
over a portion of the first and second fins, the gate structure
traversing the first and second fins, thereby separating a source
region and a drain region of the first and second fins; a first
epitaxial semiconductor layer disposed over another portion of the
first and second fins; and a second epitaxial semiconductor layer
disposed over the first epitaxial semiconductor layer, wherein the
source and drain regions of the first and second fins include a
portion of the first and second epitaxial semiconductor layers. The
source and drain regions of each of the first and second fins
defines a channel therebetween. The channel may be in contact with
the first and second epitaxial semiconductor layers. In an example,
the first and second fins include silicon, the first epitaxial
semiconductor layer includes silicon, and the second epitaxial
semiconductor layer includes silicon germanium.
[0058] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
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